This invention relates to a loop taker for sewing machines, having a hook for arresting a needle loop.
Loop takers having hooks are classified into two types, one used exclusively for household sewing machines in which the loop taker is oscillated, and the other used for industrial sewing machines and also for household sewing machines in recent years in which the loop taker is rotated in a horizontal plane. The manufacture of each type has involved a number of steps. For example, in the type in which the loop taker is rotated, roughly speaking its manufacture involves welding a ring-like metal part and a bottom lid to unite them, grinding a notch to form a hook, and removing burrs and buffing the surface to ensure smooth slide movement of the yarn, the operation amounting to as many as 30 steps. Similarly, the type in which the loop taker is oscillated requires a large number of manufacturing steps. Such largeness of the number of steps increases the manufacturing cost of the shuttle race and body assembly, and the larger the number of steps, the greater the percentage occurrence of reject parts, which, in turn, increases the manufacturing cost of the shuttle race and body assembly.
This problem can be solved by molding the loop taker of resin. Since the production of loop takers can be effected in one steps, the manufacturing cost is reduced to a large extent. Further, the molding of loop takers of resin provides the following advantages in addition to the reduction of manufacturing cost.
First, vibration and noise produced by the rotating or oscillating movement of the loop taker are absorbed. Such vibration and noise are produced when the needle loop passing over the loop taker comes out from between the loop taker and the shuttle driver, which is driven to oscillate the loop taker, at which time the two strike against each other, or when the needle loop comes out from between the bobbin case, which is carried by the loop taker, and the retainer of the bobbin case in order to pass over the bobbin case.
Second, the inertia force is reduced because of the reduction in weight.
Third, if a resin of satisfactory lubrication is used, this eliminates the need for oiling and produces no creak. If a resin having a low coefficient of friction is used, the loop taker will move smoothly.
However, a loop taker made of resin, as compared with one made of metal, has a disadvantage that its strength and wear resistance are low. This has been a major cause of baffling a realization of its practical use. This problem must be solved before a loop taker make of resin can be put to practical use.
The rotating type loop taker has another problem which follows.
When it is needed to replace the loop taker or to clean it, the dismounting and mounting of the loop taker is not easy. The need of replacing the loop taker arises (1) when the timing between the loop taker and the needle goes out of order or the needle is bent and hence the needle point strikes against the hook and thereby breaks or damages the hook, (2) when the loop taker is rusted, (3) when the yarn does not slide smoothly, and (4) when the loop taker is worn out. The need for cleaning the loop taker arises (1) when waste pieces of yarn have accumulated, and (2) when the yarn tends to be contaminated with lubricating oil or the like.
For example, in the type shown in FIG. 1 in which a loop taker 1 is rotated in a horizontal direction, the removal of the loop taker 1 would involve the following operation. First, a base cover 2 may be removed to loosen fixing screws 3 and then a driver shaft 4 may be withdrawn. However, since the loop taker 1 is generally provided with a gear 5 integral therewith, the withdrawal of the loop taker together with said gear 5 would be obstructed by such parts as a feed mechanism 6, a lower shaft 7, and a gear 8 meshing with the gear 5 and fixed on the lower shaft 7. Therefore, the downward withdrawal of the loop taker 1 is impossible. On the other hand, the upward withdrawal of the loop taker 1, which is not obstructed by the aforesaid machine elements, is not so easy since the space defined below the head 9 of the sewing machine is narrow.